Magnetization reversal in arrays of individual and coupled Co-rings

The magnetization behavior of arrays on 10 mum Co rings has been studied using magnetometry, magneto-optical imaging, and Lorentz microscopy. Square arrays of individual rings and arrays of chains of interacting, touching rings have been investigated. In fields transverse to the chains the switching of the rings occurs always in pairs. This coupling introduces a broad distribution of switching fields and correspondingly a broad magnetization loop. Lorentz microscopy reveals that the switching for both, the isolated and the coupled rings, occurs through the formation of a buckled state, and the nucleation and propagation of a vortex domain wall. (C) 2003 American Institute of Physics.